Heater and contact structure therefor



Mam}! 1966 J. J. FANNON, JR

HEATER AND CQNTACT STRUCTURE THEREFOR Filed Dec. 29, 1961 ATTORNEYSnected to a copper or copper alloy contact.

United States Patent 3,242,315 HEATER AND CONTACT STRUCTURE THEREFORJohn J. Fannon, Jr., Grosse Pointe Park, M1ch., assignor to HuppCorporation, Cleveland, Ohio, a corporation of Virginia Filed Dec. 29,1961, Ser. No. 163,144 6 Claims. (Cl. 219356) The present inventionrelates to improvements in electrically powered radiant heaters andcontact structures therefor and more particularly to improvements in thestructure of electrical contacts intended for high temperatureoperation.

The specific present commercial application of the present invention isin the contact structures for the radiants or heating elements ofinfra-red generating electrically powered heaters. Such heaterscustomarily utilize heating elements of the quartz type. These heatingelements, when utilized in groups and arranged for cross-irradiation,have a surface temperature in the order of 1600 F. at their radiantportions, typically have 1000 or 1500 watt power input requirements andmay be utilized singly or in groups of two, four or more.

Such heating elements, at their opposite ends, have electrical contactferrules or caps made of a heat resistant electrically conductive alloyto resist deterioration under the high operating temperatures involved.The alloy used is a stainless steel containing nickel, chromium andiron. In operation, the ends of the heating elements operate attemperatures in the order of 800 F. to 1000 F. In the heater assembly,the ferrules or end caps are pressed between the arms of housing mountedcontact clips to form an electrically conductive pressure contact and asupport for the heating element. customarily, these contact clips aremade of a copper alloy such as beryllium copper or brass to provide thegood electrical conductivity and resilience required in spring biasedpressure contacts such as this.

It has been found, however, that with the stainless steel of theferrules or caps in pressure contact with copper alloy contact clips andoperating at a temperature in the order of 800 F. to 1000 F., the copperalloy will rapidly deteriorate. Similar deterioration in copper alloycontact elements results when a Nichrome wire is con- Nichrome is alsoan alloy containing nickel, chromium and iron. The exact nature of thisdeterioration is not fully understood. It seems to be either anoxidation or electrolytic reaction stimulated by high temperature andhigh electrical current flow dependent upon the relative positions ofthe metals involved in the electromotive series. The result is that thedeterioration of the copper alloy rapidly produces a powder, greatlyincreases the resistance of the contact between the connected parts,rapidly reduces the operating efficiency of the heating unit andresults, in many instances, in damage to the component parts.

The primary object of the present invention is, therefore, to provide animproved electrical infra-red heater and contact structure therefor inwhich a contact element formed of a nickel-chromium-iron alloy is inpressure contact with a copper alloy contact element but in which thecopper alloy contact element will not deteriorate under elevatedoperating temperatures.

More specifically, it is an object of this invention to provide animproved electrical contact which is com patible with complementaryelectrical contacts formed of a nickel-chromium-iron alloy such asstainless steel or Nichrome, particularly one which is in the form of aspring element which can be biased against the nickelchromium-iron alloycontact element and which will not deteriorate under temperatures in theorder of 800 F. to 1000 F.

Still more specifically, it is an object of this invention to provide animproved copper alloy contact clip which may be utilized with stainlesssteel or other nickel-chromium-iron alloy contact ferrules or capswithout deterioration of the copper alloy at elevated temperatures.

A further specific object of this invention is to provide anickel-plated copper alloy contact clip.

These and other objects of the present invention will become more fullyapparent by reference to the appended claims and as the followingdetailed description proceeds in reference to the accompanying drawingswherein:

FIGURE 1 is a perspective view from beneath of a typical space heaterutilizing quartz heating elements and embodying the contact structure ofthe present invention;

FIGURE 2 is a perspective view from above of the space heater of FIGURE1;

FIGURE 3 is a fragmentary longitudinal sectional view through one end ofthe heater of FIGURE 1 illustrating in elevation the heating elementmounting and contact structures; and

FIGURE 4 is a fragmentary sectional view taken substantially along theline 44 of FIGURE 3.

As is shown in FIGURES 1 and 2, the space heater there illustratedcomprises a housing 10 having a downwardly facing opening 12 withinwhich is located a plurality of heating elements or radiants of thequartz type designated 14, 16, 18 and 20 backed by a reflector 22 andhaving a blower 24 on the top thereof. Blower 24 supplies air to coolthe reflector 22 by forced distribution of air through the chamberdefined between the upper surface of the reflector 22 and the top wallof the housing 10. The detailed structure of the heater 10 forms no partof the present invention but, if further details are found to benecessary to an understanding of the present invention, reference ismade to co-pending application Serial No. 163,256, filed on Dec. 29,1961, by John I. Fannon, Jr., Robert J. Fannon and Gordon B. Moody forSpace Heater.

Referring now to FIGURES 3 and 4, each of the quartz radiants or heatingelements such as 14 has at each of its ends a metal cap or ferrule 26which, in order to withstand the heat involved (800 F. to 10'00 F.), isformed of a suitable nickel-chromium-iron alloy material such asstainless steel. When the radiant 14 is installed, cap 26 is pressedupwardly between the depending arms 28 and 30 of the contact clip 32.Contact clip 32 is mounted by a suitable terminal assembly 34comprising, in the illustrated structure, complementary and interfittingceramic insulators 36 and 38 and a bolt 40 mounted upon a suitablesupport plate 42 fixed relative to the housing 10. The diameter of cap26 is slightly larger than the normal spacing between arms 28 and 30 sothat the arms 28 and 30 are in pressure contact with the exteriorsurface of the cap 26 due to the resilience of arms 28 and 30 and of theinterconnecting portions of the clip 32. The form of the clip 32, asillustrated, is conventional. Such clips are customarily formed of acopper alloy such as brass, beryllium copper and the like. While suchcontacts are satisfactory for use at low temperatures, when placed incontact with a complementary contact element formed of anickel-chromiumiron alloy such as stainless steel or Nichrome andsubjected to elevated temperatures, a powder will rapidly developbetween the engaged surfaces of the contact elements which increases theelectrical resistance therebetween to unacceptably high levels.

I have found that by interposing between the copper alloy and thenickel-chromium-iron alloy a layer of nickel thereon. V by the nickelplating from contaminants and atmosphere,

in the form of a plating upon the copper alloy contact no suchdistintegration of the contacting surfaces occurs. For this reason, theclip 32 is plated, at least on the \surfaces of its arms 28 and 30 whichcontact the ferrule or cap 26, with a layer of substantially purenickel. This layer of nickel eliminates deterioration of the contactclips 32. The reason it does is not clear. It does form a layer on thecopper alloy element of a metal which is a constitutent of the alloy ofwhich the other contact is for-med.

Also, as is apparent from reference to the electropotential series ofmetals, in a normal ionic solution at 25 C., chromium has a potential of+.557 volt, iron +.441 volt, nickel +231 volt, and copper -.344 volt.Thus, the potential difference across the surfaces in pressureengagement in the prior art contact structure is .901 volt betweencopper and chromium, .785 volt between copper and iron and .575 voltbetween copper and nickel. With the contact structure constructed inaccord with the present invention, the potential difierence across thesurfaces in pressure engagement is only .326 volt between nickel andchromium and only .210 volt between nickel and iron. The .575 voltpotential difference between copper and nickel exists at the boundarysurfaces between the copper alloy clip and the nickel plating Since thisboundary surface is fully shielded no material current flow results.

While at low temperatures these factors are not significant, at elevatedtemperatures in the order of 800 F. to 1000 F., they apparently becomequite important.

Whether these factors are the controlling factors involved or the factthat the melting point of nickel is substantially higher than that ofcopper and its alloys is an involved factor is not presently known. Itis clear, however, that nickel plating of the copper alloy contact doesprevent its deterioration at elevated temperatures and high current flowwhen in pressure contact with a nickel-chromium-iron alloy. From theforegoing it should be apparent that other metals similar to nickel inthat they do not melt at temperatures below 1000 F. and are at least ashigh in the electromotive series as nickel may be used in the place ofnickel and are within the scope of this invention;

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. An air exposed pressure contact structure comprising a firstelectrical contact in pressure engagement with a second electricalcontact wherein said first electrical contact is a nickel-chromium-ironalloy and said second s s ita smt q a copper base alloy ving a. la er 9tsubstantially pure nickel on at least the portion of said copper basealloy contact in pressure engagement with said first contact to preventdeterioration of the copper base alloy at temperatures in the order of800 F. to 5 1000 F.

2. In an air exposed electric radiant heating unit having an electricalradiant heating element and a power supply means including a pressurecontact structure, the improvement wherein said pressure contactstructure comprises a first electrical contact in pressure engagementwith a second electrical contact wherein said first electrical contactis a nickel-chromium-iron alloy and said second electrical contact is acopper base alloy having on at least the portion of said opper basealloy contact in pressure engagement with said first contact a layer ofmetal having a melting point greater than 1000" F. and an electromotivepotential at least as high as nickel to prevent deterioration of thecopper base alloy at temperatures in the order of 800 F. to 100'0 F.

3. The heating unit of claim 2 wherein said metal is nickel.

4. An electrically powered infra-red radiant heater comprising:

(a) a reflector equipped housing,

(b) a heating element,

(c) air exposed means mounting said heating element upon said housingincluding a pair of heating element supporting contact structures eachembodying a copper base alloy contact element fixed to said housing anda nickel-chromium-iron alloy contact element fixed to said heatingelement, and

(d) a substantially pure layer of nickel on at least the portion of saidcopper base alloy contact in pressure engagement with said first contactfor preventing deterioration of said copper alloy contact element underthe influence of heat generated by said heating element.

5. The heater defined in claim 4 wherein said nickelchromium-iron alloyis a stainless steel.

6. The heater defined in claim 4 wherein said copper base alloy isbrass.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS3/1937 France.

REST-1A5]; M, WOOD, Primary Examiner.

1. AN AIR EXPOSED PRESSURE CONTACT STRUCTURE COMPRISING A FIRSTELECTRICAL CONTACT IN PRESSURE ENGAGEMENT WITH A SECOND ELECTRICALCONTACT WHEREIN SAID FIRST ELECTRICAL CONTACT IS A NICKEL-CHROMIUM-IRONALLOY AND SAID SECOND ELECTRICAL CONTACT A COPPER BASE ALLOY HAVING ALAYER OF SUBSTANTIALLY PURE NICKEL ON AT LEAST THE PORTION OF SAIDCOPPER BASE ALLOY CONTACT IN PRESSURE ENGAGEMENT WITH SAID FIRST CONTACTTO PREVENT DETERIORATION OF THE COPPER BASE ALLOY AT TEMPERATURES IN THEORDER OF 800*F. TO 1000*F.